Container

ABSTRACT

A portable container ( 10 ) for receiving contents for transport while regulating the temperature of the contents includes a combined heater and/or cooler in the form of a Peltier effect device ( 50 ), a removable inner receptacle ( 70 ) for receiving the contents, an air gap around the outside of the inner receptacle, and a control unit ( 62 ) for controlling the Peltier effect device so as to regulate the temperature of the air around the outside of the inner receptacle and thereby regulate the temperature of the contents of the inner receptacle. The control unit can have a temperature logging system for recording the temperature history of the contents of the container.

The present invention relates to a container.

The increasing incidence of organ transplants, and the increasing use oftemperature-sensitive drugs in the treatment of disease in both humansand animals, has led to a need for a reliable portable container forsuch organs and drugs. It is currently usual for organs and drugs to betransported in boxes packed in ice. This is unsatisfactory for a numberof reasons.

Firstly, the use of ice means that the highest temperature which theorgans or drugs can be kept at is freezing point, or 0° C. Ice crystalswill start forming at this temperature, and the growth of these icecrystals can damage the cells of an organ being transported fortransplant, unless steps are taken to avoid this. In addition, 0° C. maynot be the optimum temperature at which drugs should be kept.

Secondly, the ice will melt in time, and so the temperature at which thedrugs or organs will be held is not steady. It may be necessary toreplenish the ice during transportation.

To avoid these problems, it is desirable to provide a container withsome means of regulating its temperature, for example with a Peltiereffect device which can heat or cool the contents and a control unit.

A further use of medical containers is in the transport of samples ofinfectious or contaminated material. For example, samples of suchmaterial may need to be taken to a laboratory for analysis. It isfrequently necessary to maintain such samples at given temperatures, toensure that bacteria in the samples are still alive when they reach thelaboratory and can then be cultured and identified. However, it will beappreciated that transport of such samples poses a number of problems.In particular, following such transportation, it is necessary to ensurethat the container is properly sterilized afterwards, to preventcross-contamination. This can be done by washing or autoclaving, but itwill be understood that these methods may not be ideally suited tocleaning a Peltier device.

According to a first aspect of the invention, there is provided aportable container for receiving contents for transport whilstregulating the temperature of the contents, the portable containercomprising heating and/or cooling means in the form of a Peltier effectdevice, a removable inner receptacle for receiving the contents, an airgap around the outside of the inner receptacle, and a control unit forcontrolling the Peltier effect device so as to regulate the temperatureof the air around the outside of the inner receptacle and therebyregulate the temperature of the contents of the inner receptacle.

The heating and/or cooling means may comprise a heating means only, or acooling means only. However, it is preferred that both heating andcooling means are provided.

The control of the temperature of the air in the air gap around theinner receptacle enables regulation of the temperature of the contentswhilst still permitting the inner receptacle to be removed. Removal ofthe inner receptacle is useful, for example enabling it to be washed orautoclaved. In addition, when removed the inner receptacle may be placedin a refrigerator. It may thus be refrigerated to the desiredtemperature, before being placed into the main container, which can thenbe closed and activated to regulate the temperature of the contents ofthe inner receptacle. This reduces the amount of power used by theportable container, as it is only necessary to keep the contents cold,rather than having to cool them down initially. If for example thecontainer is powered by a battery, then the length of time for which thecontainer can keep its contents cold, and thus the length of journeywhich can be undertaken, can be increased.

The portable container can be used to carry drugs, tissue samples,organs for transplant, or indeed any other material which must betransported at a given temperature.

The container will generally have an outer housing, with the air gapbeing defined between the outer housing and the inner receptacle. Theouter housing may comprise a base portion and a lid portion.

A fan is preferably provided to assist air circulation in the air gap.This is advantageously provided adjacent to the Peltier device, both forexample being located in a lid portion of the container.

Preferably, the container comprises projections which extend from theouter housing of the container to support the inner container. Air canthen circulate between the projections around the inner receptacle. Inaddition, the projections help to locate the inner container securely inthe main container.

Preferably, the control unit of the container is arranged to store adesired temperature for the contents of the container, to receive asignal from a temperature sensor located within the container, and togenerate a signal to control the Peltier effect device. From acomparison of the sensed temperature signal with the desiredtemperature, the control unit decides whether to operate the Peltiereffect device, and in what sense (heating or cooling the interior of thecontainer). The temperature sensor is preferably arranged to sense thetemperature in the air gap. More than one sensor may be provided, e.g.one above the inner receptacle and one below.

The temperature at which the contents of the container are to bemaintained can be set permanently in the control unit. However, as thecontainer may be used with different materials, it is preferred that thetemperature at which the contents of the container are to be maintainedis entered into the control unit.

This information can be entered in any suitable manner. In a preferredversion, a keypad is mounted on the container for entering the desiredtemperature. However, the keypad may be susceptible to damage, and soalternatively or additionally, the container may comprise anelectromagnetic or ultrasonic receiver , and the temperature is setusing an external transmitter. In a further version, the container maybe connectible to a computer, either directly or via a modem, and thisis used to set the temperature.

It may be important that the desired temperature, once set, is notchanged without authorization, and thus it is preferred that the controlunit includes means for verifying the status of a user before thetemperature at which the contents of the container are to be maintainedis set. If a key-pad is used, then it may be necessary to enter a code(such as a PIN) before the set temperature can be changed. Codes canalso be used if a radio or a computer system is used to enter theinformation. A card system, for example using swipe cards, or a systemwhere a key has to be inserted into a lock before the set temperaturecan be modified, could also be used.

It is also generally desirable to know the temperature history of thecontents of the container.

In previous containers, there is no guarantee that the organs or drugshave not been damaged during transit by exposure to inappropriatetemperatures, as there is no record of the temperatures to which theyhave been exposed. Thus, it is preferred that the control unit alsocomprises a temperature logging system, said temperature logging systemproviding means to verify the temperature history of the container.

This feature is considered to be of independent inventive merit, and soaccording to a further aspect of the invention, there is provided aportable container for receiving contents for transport whilstregulating the temperature of the contents, the portable containercomprising heating and/or cooling means, and a control unit forcontrolling the heating and/or cooling means so as to regulate thetemperature of the contents of the container, said control unitcomprising a temperature logging system, said temperature logging systemproviding means to verify the temperature history of the contents of thecontainer.

The temperature logging system can take a number of forms. For example,a device similar to a tachograph can be used, to sample the temperatureat given intervals and make a mark on a record sheet. The marks could(as in a tachograph) require interpretation in order to be understood.However, in a preferred version, the temperature logging system samplesthe temperature at intervals, and prints the sampled temperature. It isthen only necessary to check the printout to see whether the settemperature has been adhered to. Alternatively, the temperature loggingsystem can be provided with a memory which stores data concerning thetemperature history. The information in this memory can be accessed bysuitable means such as a computer using a modem, optionally by a remotelink, and displayed. As an alternative, the computer can be programmedto check the data itself, and give a simple “safe/unsafe” output.Whatever method is chosen, the temperature history of the contents canbe checked when the container arrives at its destination, and therecipient can thus immediately verify whether the contents have beendamaged by exposure to inappropriate temperatures during transit. Thecontents of the container are thus immediately verifiable.

Of course, while it is useful to know that the material beingtransported has spoiled as a result of being exposed to inappropriatetemperatures, it would be better for the material not to spoil at all,to avoid wastage. This is particularly important in the case of organsfor transplant. Thus, in a preferred embodiment, the control unitgenerates an alarm signal if the temperature in the container strays toofar from the set temperature. The meaning of “too far” will of coursedepend on the material being transported, but 3° C. is a typical amount.This alarm signal may take the form of a light on the container or anaudible signal, which would alert a person travelling with the containerthat something is amiss.

Alarm signals can also be generated if the latches holding the containerclosed are detected as being opened, as this can indicate that thecontainer, and possibly the contents thereof, have been tampered with.

The container can be powered in any suitable manner. However, as thecontainer is intended to be portable, the power for the Peltier device,the control units and the fan motors is preferably derived from abattery, more preferably a rechargeable battery. It is preferred that aback-up power source is also provided, in the form of a second battery,so that even if the main battery is exhausted the container can stillregulate the temperature of its contents. An alarm signal can begenerated on failure of the main battery, and a further different alarmsignal can be generated when the back-up battery falls below apredetermined proportion of its capacity.

Further, it is preferred that the container be sufficiently robust towithstand impacts and shock loading. It is inevitable that accidentswill occur, and that containers will be dropped from heights, hit and soon. However, Peltier devices are relatively fragile, and must beprotected from severe impacts.

Thus, it is preferred that the Peltier device is mounted in a block ofelastomeric material. The provision of this elastomeric element helps toreduce the decelerations undergone by the Peltier device, and thusreduces the shock loads thereon.

This feature is considered to be of independent inventive merit, and soaccording to a further aspect of the present invention, there isprovided a portable container having heating and/or cooling means in theform of a Peltier effect device, wherein the Peltier device is mountedin a block of elastomeric material which is in turn mounted to a housingof the container.

It is further preferred that the Peltier device is connected to an innerheat sink facing the interior of the container and an outer heat sinkfacing the exterior of the container, the heat sinks being clampedtogether by clamping means passing through the heat sinks and theelastomeric member. The Peltier device, the heat sinks and theelastomeric member then form a single unit, and the heat sinks and thePeltier device will undergo the same decelerations. It is desirable thatthe heat sinks remain in intimate thermal contact with the Peltierdevice, to enable it to function properly, and this feature reduces therisk that they may be jolted apart.

The clamping means can take any suitable form. However, if there is apath of conduction from the inner heat sink to the outer heat sink, thenthe insulative properties of the container will be compromised, asindeed will the efficiency of the Peltier device. Thus, it is preferredthat the clamping means is formed from a plastics material. In aparticularly preferred embodiment, the clamping means are nylon bolts.

Of course, if the container is to keep the contents at a giventemperature, it is desirable that it have a thermally insulating outerhousing, to prevent variations in the external temperature fromaffecting the temperature of the contents.

A number of ways of constructing thermally insulating containers areknown. For example, a Dewar flask has a double-walled construction. Thespace between the walls is evacuated to provide a vacuum, and the sidesof the walls facing the vacuum are silvered. It is also known to usethermally insulating material such as foamed polymer materials such aspolyurethane in the walls of containers, to reduce heat conductionacross the wall.

It is known to use vacuum panels for thermal insulation. These panelscomprise a layer of thermally insulating material enclosed within anevacuated flexible cover, which includes an aluminium layer. When suchpanels are used to insulate containers, they are normally placed in thehollow walls of the container to reduce the heat passing through thewalls by conduction. However, the presence of air in the hollow wallsstill allows heat transfer through convection.

Preferably, the container comprises an outer housing in the form of aninner wall and an outer wall defining a space therebetween, wherein thespace between is the inner and outer walls is at least partiallyevacuated and is occupied by a solid thermally insulating material.

The inner and outer walls thus define the space which is at leastpartially evacuated and occupied by the insulating material, in additionto their other function as container walls.

The presence of the thermally insulating material reduces the amount ofheat which is transferred through the container walls by means ofconduction. Further, heat transfer by means of convection is reduced bythe at least partial evacuation of the space between the inner and outerwalls. Of course, the greater the degree of evacuation, the less heat istransferred by convection.

This feature is also considered to be of independent inventive merit,and so according to a further aspect of the present invention there isprovided a container comprising an inner wall and an outer wall defininga space therebetween, wherein the space between the inner and outerwalls is at least partially evacuated and is occupied by a solidthermally insulating material.

Such a container can removably hold contents which are to be thermallyinsulated from the environment, and will therefore generally have a mainbody and a closure.

The insulating material can be in the form of a powder. However, it isthen necessary for the inner and outer walls to be relatively rigid andstrong. Accordingly, it is preferred that the insulating material isrigid. The insulating material will then contribute to the structuralintegrity of the container as a whole. One suitable insulating materialis compacted microporous silica.

If a rigid insulating material is used, it will normally be shaped tooccupy the space between the inner and outer walls, for example by beingmoulded or machined to the required shape.

In a preferred embodiment, the insulating material hinders the passageof infra-red radiation. This can be done by absorbing, reflecting orscattering the infrared radiation, and reduces the amount of heattransferred through the walls of the container by means of radiation.

In a further preferred embodiment, the outer wall is metallized. Themetallized layer will attenuate any radiation passing through it, andthis also helps to reduce the amount of heat transferred through thewalls of the container by means of radiation. Using a metallized outerwall with an insulating material that absorbs infra-red radiation canreduce the amount of heat transferred to very low levels.

Preferably, it is the inner surface of the outer wall that ismetallized. This protects the metallized layer from abrasion and so on,which it would be subjected to if it was on the outer surface of theouter wall, and thus prolongs its lifespan.

As an alternative to, or additionally to providing a metallized layer,the outer wall may include a metallic foil layer. The outer wall can beformed as a laminate, incorporating a metallic foil layer.

It is further preferred that the inner wall of the container ismetallized. When it is desired to maintain the contents of the containerat above ambient temperature, it is important to reduce heat losses fromthe contents, and metallizing the inner wall reduces the amount ofinfra-red radiation passing through the inner wall.

Alternatively or additionally, the inner wall may include a metallicfoil layer, and may be formed as a laminate incorporating a metallicfoil layer.

The metallization or the metallic foil layer of the inner or outer wallscan be provided with means for making an electrical connection toprovide an electrostatic shield. This can then serve to shield anyelectrical equipment inside the container from electrical interference.It is envisaged that the insulated container will include an electricalcooling and/or heating means, and the switching of this means couldcause interference if it were not shielded.

The space between the inner and outer walls can be at least partiallyevacuated and then permanently sealed. However, as any material used toform the inner and outer walls will be permeable to some degree, it ispreferred that some means of restoring the vacuum be provided.Accordingly, in a further preferred embodiment, there is provided apassageway to allow the space between the inner and outer walls to becommunicated with a region outside of the space. The passageway canallow the space between the inner and outer walls to be connected to apressure gauge, a vacuum pump or the like. The vacuum in the spacebetween the inner and outer walls can then be checked by means of apressure gauge, and if the vacuum has become overly degraded, as aresult of excessive gas permeation through the inner and outer walls,then it can be restored using the vacuum pump.

Of course, means must be provided to ensure that there is no leakage atthe passageway. This could be done by providing a plug in thepassageway. However, it is preferred that the passageway be providedwith a valve, which is normally closed. The valve can then be openedwhen a pressure gauge, vacuum pump or the like has been connected.

The passageway can be provided at any convenient point on the inner orouter walls, or on e.g. an end wall which connects the inner and outerwalls. However, if the passageway is in the outer wall, then there is arisk that an impact or similar could open it, for example by damaging avalve provided on the outer wall. It would be possible to recess a valvein the outer wall to reduce the risk of impact damage. However, it ispreferred that the inner wall be provided with the passageway, tosubstantially eliminate the risk of impact damage to it.

Preferred embodiments of the invention will now be described by way ofexample only and with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a first embodiment of the container in aclosed condition;

FIG. 2 is a fragmentary schematic cross-sectional view showing theconstruction of a wall of the first embodiment of the container;

FIG. 3 is a fragmentary schematic cross-sectional view showing a variantconstruction of a wall of the first embodiment of the container;

FIG. 4 is a cross-sectional view through a second embodiment of thecontainer;

FIG. 5 is a fragmentary cross-sectional view of the lid of a thirdembodiment of the container;

FIG. 6 is a plan view of a part of the lid of the third embodiment ofthe container; and

FIG. 7 is a perspective view of the same part of the lid of the thirdembodiment of the container.

A container according to a first preferred aspect of the invention isindicated by the reference numeral 10 in FIG. 1. The container comprisesa base part 12, in which the contents are accommodated, and a lid 14.The base part and the lid together form an outer housing. The lid 14 isattached to the base 12 by a hinge, clamps or the like, and thecontainer is held closed by latches 76. The container is intended tothermally isolate its contents from the outside, for example to keep thecontents cooler than outside.

The walls of the container have a sandwich construction, as is bestshown in FIG. 2. They comprise an outer wall 20, which forms theexternal surface of the container, a middle layer 30, and an inner wall40. The middle layer occupies the space between the inner and outerwalls.

The outer wall fulfils a number of functions. It is substantially gas-and liquid-impermeable. It is also important for the material formingthe outer wall to be strong, and in particular to be puncture-resistant.In order for the outer wall to meet these various criteria, aresin-bonded laminated material is used. The laminate can include layersof Kevlar (trade mark) or glass- or carbon-fibre reinforced plasticsmaterial, to provide the necessary strength. Such materials are verystrong in tension, compression and shear, and also display goodresistance to shock loads. This is important in helping avoid damage tothe container when it is dropped.

The inner surface 22 of the outer wall 20 is metallized. This can bedone by spraying, sputtering or vacuum deposition of steel or aluminium.The metallized layer reflects most of the radiation incident thereon,and attenuates the radiation passing through the outer wall 20. If themetallized layer were to be applied to the outer surface 24 of the outerwall 20 rather than the inner surface 22, then it would be subject toscratching, abrasion and the like. Any discontinuities in the metallizedlayer will allow radiation to pass through it unaffected, and this isclearly undesirable. For this reason, the metallized layer is applied tothe inner surface 22 of the outer wall 20.

Alternatively, or additionally, the laminated material can include oneor more metallic foil layers. These will not only serve to reflect andattenuate radiation, but also reduce the overall permeability to gasesof the outer layer.

One or more of the metallized or metallic foil layers can be providedwith means for making an electrical connection to provide anelectrostatic shield. This shield will function as a Faraday cage, andwill screen any interference which may otherwise be caused by electricalequipment such as heaters, coolers or thermostatic controls inside thecontainer.

The middle layer 30 comprises a porous expanded silica material, whichoccupies substantially the whole of the lateral width between the innerand outer walls (i.e. the direction transverse to the planes of thewalls). The material has a very low thermal conductivity, and serves asa thermal insulator for the container. Such a material is availableunder the name “Microtherm” from Micropore International Limited ofDroitwich, England. In addition to its thermally insulatingcharacteristics, the material is rigid and contributes to the strengthand structural integrity of the container.

The expanded silica material can also be treated to further reduce thetransmission of infra-red radiation through it. It can incorporatemetallic platelets to reflect infra-red radiation, semiconductors suchas carbon black or metal oxides to absorb infra-red radiation, and/orhigh refractive index transmitters to scatter infra-red radiation. Theseserve to make the middle layer substantially opaque to infra-redradiation. As a result, any infra-red radiation which does pass throughthe outer wall 20 will not reach the interior of the container 10.Further, the size of the pores in the expanded silica material is lessthan the mean free path of air molecules.

The inner wall 40 can be constructed in a similar way to the outer wall20, since it must also be substantially impervious to gases or liquids.However, as the inner wall 40 is less likely to be subjected to directimpacts or similar shocks, it does not require the same strength as theouter wall 20. Further, since any infra-red radiation passing into thecontainer should be prevented from passing through the middle layer 30,there is less need for the inner wall 40 to be metallized in situationswhere it is desired to maintain the temperature of the contentscontainer below ambient temperature.

Of course, where it is desired to maintain the temperature of thecontents of the container above ambient temperature (for example, toprevent freezing of the contents in extremely cold conditions), then itis preferable for the inner wall to be metallized, to prevent heatescaping from the contents through infrared radiation. Additionally,there is less need for the outer wall to be metallized in theseconditions. Of course, if the outer wall is not metallized or providedwith a metallic foil layer, then the metallized or metallic foil layerof the inner wall can be used to form an electrostatic shield asdiscussed above.

To allow the container to be used whether the temperature of thecontents is to be maintained above or below ambient temperature, boththe inner and outer walls can be metallized, to reduce heat transfer bymeans of radiation either to or from the contents of the container. Theless radiation that passes through the inner or outer walls, the lessradiation there is to be absorbed, reflected or scattered by theinsulating material, and this reduces the conductive heat transportload.

In the manufacture of the container, the inner and outer walls areformed separately. Machined blocks of the expanded silica material areloaded into the floor region and around the sides of the outer wall, andthe inner wall is then inserted.

The inner and outer walls 20, 40 are then connected together so thatthey form a gas- and liquid-impermeable envelope around the middle layer30. This can be done in a number of ways. For example, welded metallicseals can be used, although this then provides a path of heat conductioninto the container. As an alternative, preformed neoprene seals can bebonded to both the inner and outer walls, and this method of sealingsubstantially reduces heat conduction. In addition, if laminatedmaterials are used to form the inner and outer walls, these canthemselves be formed into lips and seals, which can then have anoverlaying neoprene layer applied to them to seal them fully. The use ofa neoprene layer can also enhance the sealing between the base and thelid of the container when it is closed, as the neoprene layer may bepositioned where the base and the lid abut.

To further enhance the insulating properties of the container 10, theenvelope is evacuated to a fairly high vacuum, such that the pressure ispreferably less than 0.1 mm Hg (0.13 millibars or 13 Pa). The evacuationof the envelope substantially reduces convective heat transfer throughthe middle layer. It will be appreciated that it is necessary for theinner and outer walls 20, 40 to be impervious to gases in order tocreate a vacuum inside the envelope. It will also be appreciated that,since any puncture of the envelope will lead to loss of the vacuum, itis important for the outer wall 20 in particular to be strong andpuncture-resistant.

Once the vacuum has been established, external atmospheric pressure willtend to push the outer wall inwards. Similarly, atmospheric pressureinside the container will tend to push the inner wall outwards. Thetendency for the walls to collapse towards each other is resisted partlyby the inherent strength of the walls, and partly by the presence of theinsulating material. Because the insulating material helps to resist thecompressive forces caused by atmospheric pressure, the walls may bethinner and hence more lightweight than would otherwise be the case.

A passageway 42 is provided in the inner wall 40. This passageway isprovided with a valve 44, which is normally closed. The passageway 42can be connected to a vacuum pump and the valve 44 opened to allowinitial evacuation of the space between the walls. In addition, thepassageway 42 can be connected to a pressure gauge, allowing the degreeof vacuum in the space to be checked. There will inevitably be someleakage through the inner and outer walls 20, 40, and this will tend todegrade the vacuum in the space. If a check shows that the vacuum in thespace has become too degraded, the vacuum pump can be reconnected toevacuate the space again and restore the vacuum.

As mentioned above, the expanded silica material is porous, and so thegases in the pores of the material must be removed when the spacebetween the inner and outer walls is evacuated. A small recess 32 in theexpanded silica material is shown opposite the passageway 42 in FIG. 2.This provides a greater surface area of the expanded silica material forthe vacuum to act upon, and so assists in the degassing of the material.However, the recess can be dispensed with if desired.

As mentioned above, the container 10 comprises a base 12 and a lid 14,to allow access to the contents of the container. The walls of both thebase 12 and the lid 14 are formed with a sandwich construction asdescribed above, to provide good thermal insulation. Since the base 12and the lid 14 are formed as separate parts, the lid 14 is also providedwith an opening, to allow the lid envelope to be evacuated and thevacuum in the envelope to be checked and restored if necessary.

It will thus be seen that the walls of the container 10 prevent heattransfer by all three of the normal mechanisms (conduction, convectionand radiation). Heat conduction through the wall is prevented by the lowthermal conductivity of the expanded silica material forming the middlelayer 30. Convection cannot take place as the envelope is evacuated, andso there is no fluid through which convection can occur. Heat transferthrough radiation is prevented by the metallized layer(s) of the innerand/or outer wall 40, 20, which attenuates any incident radiation, andthe presence of the materials in the expanded silica material of themiddle layer 30, which reflect, absorb and/or scatter any infra-redradiation which has passed through the outer wall 20.

In an alternative construction shown in FIG. 3, the rigid expandedsilica material can be replaced by granules of expanded silica. However,it is then necessary for the outer wall 20 to be relatively strong, andit may also be necessary to provide spacers 34 between the outer andinner layers to maintain a spacing between them. In addition, means mustbe provided to ensure that the granules are not sucked out by the vacuumpump when the space between the inner and outer walls is evacuated. Thismeans can take the form of a screen 36 across the end of the passageway42.

The container described above is intended to keep its contents at acertain temperature irrespective of ambient temperature, and may be aportable container, e.g. a food or medical container. It will beappreciated however that the wall construction is also applicable toother types of container, such as refrigerators, freezers orrefrigerated vehicles.

If the container is to be used as a portable food or medical container,then it is necessary that the temperature of the contents stays withincertain bounds. Medical materials in particular, such as organs fortransplant and certain temperature-sensitive drugs, are easily damagedby being kept at inappropriate temperatures.

In a second preferred embodiment of the invention, as shown in FIG. 4 inparticular, the container is provided with a thermoelectric module 50which exploits the Peltier effect, for heating and/or cooling thecontents of the container.

When a direct current passes around a circuit incorporating twodifferent metals, one of the junctions between the two metals is heatedand the other cooled. Which junction is heated and which is cooleddepends on the direction of the current. A similar effect arises ifcertain semiconductors are used instead of metals. This generation andabsorption of heat can be used to provide a heat pump, and the directionin which heat is pumped depends on the direction of current flow. Heatpumps using the Peltier effect are well known, and will not be describedfurther here.

In the embodiment shown in FIG. 4, a Peltier effect thermoelectricmodule 50 is mounted in the lid of the container. The module itself isconnected between an inner heat sink 52 and an outer heat sink 54, bothof which are formed from aluminium, which provides a good balancebetween thermal efficiency and light weight. The heat sinks are providedwith fins to provide an increased surface area for heat transfer. Eachheat sink is in intimate thermal contact with a face of the Peltiereffect module 50.

Both heat sinks are provided with electrically powered fans 56, 58associated therewith. The fan 56 associated with the inner heat sink 52is arranged to drive air from the inside of the container against theinner heat sink 52. Heat energy in the air is then transferred to theheat sink by forced convection, and the air is thus cooled. The fan 58associated with the outer heat sink 54 is arranged to draw atmosphericair through ducts in the lid 14 (not shown) and through the channelsbetween the fins. The air is then heated by the heat sink 54 andexhausted through a grille 60 in the top of the lid, to transfer heatfrom the outer heat sink 54 to the environment.

The Peltier effect module 50 and the heat sinks 52, 54 can be used toheat or cool the interior of the container 10. When the interior of thecontainer needs to be cooled, electricity is supplied to the Peltiereffect module 50 so as to pump heat from the inner heat sink 52 to theouter one 54. As a result, the inner heat sink is cooled, and the outerheat sink is heated. The fan 56 associated with the inner heat sink 52is driven to bring air within the container against the inner heat sink52, and this air is cooled as a result. Meanwhile, the fan 58 associatedwith the outer heat sink 58 is activated to draw air past the outer heatsink 58 and discharge it into the atmosphere. This air is heated as itgoes past the outer heat sink 54, and thus draws heat from the outerheat sink. The net effect is to discharge heat from the interior of thecontainer to the outside.

When it is necessary to heat the contents of the container, thedirection of current supply to the Peltier device 50 is reversed, sothat heat is pumped from the outer heat sink 54 to the inner one 52. Theouter heat sink 54 is cooled as a result, while the inner heat sink 52is heated. The fan 56 associated with the inner heat sink 52 drives airin the container against the inner heat sink 52 to heat the air, andthus heat the interior of the container. The air which is in contactwith the outer heat sink 54 will serve to heat it, and as a result theair outside will be cooled. There is generally no need to activate thefan 58 associated with the outer heat sink. Thus the net effect ofoperating the module in this way is to draw heat from outside of thecontainer into its interior.

The Peltier effect module 50 allows the temperature of the interior ofthe container to be varied within a range of around 60° C., allowing thetemperature of the contents to differ by up to 30° C. from the externaltemperature. For example, in tropical areas, the contents of thecontainer could be stored at 10° C. even if the outside temperature were40° C., and the contents of the container can be prevented from freezingeven if the external temperature approaches −30° C.

The decision as to whether to heat or cool the interior of the containeris made by a control unit 62, which is programmed with the desiredtemperature for the interior of the container. The control unit receivessignals from a thermostat unit 64, which is in turn connected totemperature sensors 66, 68, located on both the upper and lower surfacesof the lid, and also on the lower floor of the container (not shown).The control unit 62 compares the signals from the thermostat unit 64with the desired temperature, and decides whether to operate the Peltiereffect module 50 to heat or cool the interior of the container.

As can be seen from FIG. 4, the container includes a removable innerreceptacle 70, and it is this inner container which actually holds thematerials (drugs, organs or the like) which are transported in thecontainer 10. Use of such an inner receptacle 70 confers a number ofadvantages. For example, the inner receptacle 70 can be made so as to beautoclavable. It is then possible to carry infectious or contaminatedmaterials in the inner receptacle, and sterilize it by autoclaving.There is no need to sterilize the main container 10, as it has not comeinto contact with the infectious or contaminated material. Further, theinner receptacle 70 can be loaded with drugs and refrigerated separatelyto cool it. When it is necessary to transport the drugs, the innerreceptacle 70 can simply be placed into the main container 10 andmaintained at a low temperature by the Peltier effect module 50. Thereis no need to use the Peltier effect module to carry out the initialcooling of the inner receptacle or its contents.

The walls and floor of the base 12 and the lid 14 of the container 10form an outer housing and preferably have the type of thermal insulationdescribed in relation to FIGS. 1 to 3.

The inner receptacle is supported in the outer container on posts 72, 74projecting inwardly from the walls and floor of the base 12 of thecontainer 10. Posts may also project downwardly from the inner surfaceof the lid 14, although these are not shown. The purpose of the posts isto ensure that air can circulate in the gap around the exterior of theinner receptacle 70. In addition, the posts projecting downwardly fromthe lid bear on the top of the inner receptacle 70, and ensure that itis properly located in the main container 10 and cannot openaccidentally.

Further, the container 10 is provided with lashing points 78, whichallow it to be secured to a vehicle.

It will be appreciated that the temperature inside the inner receptacle70 should preferably be as spatially uniform as possible, in otherwords, “hot spots” are to be avoided.

In order to avoid such hot spots, the air inside the main container 10is circulated around the inner receptacle 70, so that the whole of theoutside of the inner receptacle is kept at a generally uniformtemperature. This circulation is achieved in part by the fan 56associated with the inner heat sink 52, and in part (when the interiorof the container is being cooled) by colder air moving downwardly fromthe inner heat sink 52, displacing warmer air upwards. It is alsopossible for the inner receptacle 70 to be formed with openings, so thatair can then be circulated through it; however, it is then not usuallypossible to carry infectious or contaminated material, as there is arisk that they will leak into the main container 10.

The temperature at which the contents of the container are to bemaintained can be entered into the control unit 62 in any suitablemanner, and a number of alternatives are given in the introduction. Inaddition the control unit can include a temperature logging system, andcan generate alarm signals if the set temperature is exceeded or if thelatches holding the container closed are opened, as described above.

As the container is intended to be portable, the power for the Peltierdevice 50, the control unit 62 and the fan motors is derived from abattery (not shown). The battery is rechargeable, and can be rechargedthrough power leads 79. For convenience, the battery is provided in thelid of the container. A back-up power source is also provided, in theform of a second battery (not shown), so that even if the main batteryis exhausted the container can still regulate the temperature of itscontents. The control unit generates an alarm signal on failure orexhaustion of the main battery, and a further different alarm signalwhen the back-up battery falls below a predetermined proportion of itscapacity.

As will be appreciated, the medical container has a number ofapplications. Its robustness and ability to function in a wide range oftemperature conditions allows it to be used in areas where more delicaterefrigerated containers are not suitable.

However, Peltier effect modules are generally relatively fragile, andshould not be exposed to high decelerations. High decelerations canresult when the container is dropped, subjected to impacts or the like.It is thus necessary to ensure that the Peltier effect module 50 in thecontainer is not exposed to high decelerations when the container as awhole is.

This is achieved in the embodiment shown in FIGS. 5 to 7 by placing thePeltier effect module 50 in a flexible structure 80, which absorbs thedeceleration and protects the module from damage. A cross-section of apart of the lid 14 of the container is shown in FIG. 5. Most of the lidis formed from panels employing vacuum technology, as previouslydescribed. However, a hole is formed in the centre of the lid, and theedges of the hole are formed from the inner and outer walls of thevacuum panels, which are formed into projecting tongues 82 as shown.

A frame-shaped elastomeric member 84 is positioned in the hole, and themember is best shown in FIGS. 6 and 7. As will be seen, the edges of theframe are formed with grooves 86 , and these grooves accommodate thetongues 82 of the vacuum panels to locate the member in place. Thecentre of the frame-shaped member 84 is sized to accommodate the Peltiereffect module 50.

The inner and outer heat sinks 52, 54 are attached to the top and bottomof the Peltier effect module 50, and are located in place relative tothe frame-shaped member by nylon bolts 88, which pass through both ofthe heat sink members 52, 54 and the frame-shaped member 84. The boltsare secured in place by nylon nuts 90. Nylon nuts and bolts are used toprevent there being a direct path of good heat conduction between theinner and outer heat sinks, which would arise if metallic bolts were tobe used.

As shown in FIGS. 6 and 7, a channel 92 is formed in the upper surfaceof the frame-shaped member 84 to accommodate the power leads linking thePeltier effect module and the fan motors to the power supply.

The elastomeric member will absorb shock loads applied to the containeras a whole, and reduces the deceleration experienced by the Peltiereffect module. Containers with the Peltier effect module mounted in sucha member have greatly improved resistance to shock and impacts.

What is claimed is:
 1. A portable container for receiving contents fortransport while regulating the temperature of the contents, the portablecontainer comprising heating and/or cooling means in the form of aPeltier effect device, a removable inner receptacle for receiving thecontents, and a control unit for controlling the Peltier effect device;characterized in that the inner receptacle occupies most of the space inthe container, with an air gap around substantially the entire peripheryof the removable inner receptacle, and in that the control unit controlsthe Peltier effect device so as to regulate the temperature of the airaround the outside of the inner receptacle and thereby regulate thetemperature of the contents of the inner receptacle.
 2. A container asclaimed in claim 1, comprising projections which extend from an outerhousing of the container to support the inner container.
 3. A containeras claimed in claim 1, wherein said control unit is arranged to store adesired temperature for the contents of the container, to receive asignal from a temperature sensor located within the container, and togenerate a signal to control the Peltier effect device.
 4. A containeras claimed in claim 3, wherein a keypad is mounted on the container forentering the desired temperature.
 5. A container as claimed in claim 3,wherein the container comprises an electromagnetic or ultrasonicreceiver, and the desired temperature is set using an externaltransmitter.
 6. A container as claimed in claim 3, wherein the containeris connectible to a computer for setting the desired temperature.
 7. Acontainer as claimed in claim 3, wherein said control unit generates analarm signal if the temperature in the container strays too far from thedesired temperature.
 8. A container as claimed in claim 1, wherein saidcontrol unit comprises a temperature logging system, said temperaturelogging system providing means to verify the temperature history of thecontainer.
 9. A container as claimed in claim 8, wherein saidtemperature logging system is arranged to sample the temperature atintervals, and to print the sampled temperatures.
 10. A container asclaimed in claim 9, wherein a backup power source is provided.
 11. Acontainer as claimed in claim 10, wherein the Peltier device isconnected to an inner heat sink facing the interior of the container andan outer heat sink facing the exterior of the container, the heat sinksbeing clamped together by clamping means passing through the heat sinksand the elastomeric member.
 12. A container as claimed in claim 11,wherein the clamping means are nylon bolts.
 13. A container as claimedin claim 12, wherein the insulating material is rigid.
 14. A containeras claimed in claim 13, wherein the inner surface of the outer wall ismetallized.
 15. A container as claimed in claim 12, wherein theinsulating material hinders the passage of infra-red radiation.
 16. Acontainer as claimed in claim 12, wherein the outer wall is metallized.17. A container as claimed in claims 12, wherein the outer wall includesa metallic foil layer.
 18. A container as claimed in claim 12, whereinthe inner wall is metallised.
 19. A container as claimed in claim 12,wherein the inner wall includes a metallic foil layer.
 20. A containeras claimed in claim 19, wherein the passageway is provided with a valve,the valve normally being closed.
 21. A container as claimed in claim 12,comprising a passageway to allow the space between the inner and outerwalls to be communicated with a region outside of the space.
 22. Acontainer as claimed in claim 21 or 20, wherein the inner wall isprovided with the passageway.
 23. A container as claimed in claim 1,wherein the power for the heating and/or cooling means and the controlunit is derived from a battery.
 24. A container as claimed in claim 1,wherein the heating and/or cooling means is mounted in a block ofelastomeric material.
 25. A container as claimed in claim 1, comprisingan outer housing in the form of an inner wall and an outer wall defininga space therebetween, wherein the space between the inner and outerwalls is at least partially evacuated and is occupied by a solidthermally insulating material.
 26. A container as claimed in claim 25,wherein the metallisation or the metallic foil layer is provided withmeans for making an electrical connection to provide an electrostaticshield.
 27. A portable container having heating and/or cooling means inthe form of a Peltier effect device, wherein the Peltier device ismounted in a block of elastomeric material which is in turn mounted to ahousing of the container.
 28. A container as claimed in claim 27,wherein the clamping means is formed from an insulating material.